A fuel cell is arranged to produce electricity through a process for obtaining water by causing hydrogen and oxygen to react utilizing a principle opposite the water electrolysis. Generally, fuel gas is replaced by hydrogen, and air or an oxidant gas is replaced by oxygen.
Such fuel cell is known from, for example, Japanese Patent Laid-Open Publication No. 2000-123848 entitled “Fuel Cell”. The known fuel cell has a cell as shown in exploded perspective in FIG. 24 hereof
As shown in FIG. 24, an anode side electrode 202 and a cathode side electrode 203 are mated with an electrolytic film 201. A unit fuel cell (cell module) 200 is provided by sandwiching the afore-mentioned by a first separator 206 and a second separator 207 via gaskets 204, 205.
More specifically, the first separator 206 has on a surface 206a thereof a first flow path 208 for allowing passage of a fuel gas while the second separator 207 has on a surface 207a thereof a second flow path 209 for allowing passage of an oxidant gas, so that the fuel gas and the oxidant gas are guided to the electrolytic film 201.
Because the electrical output produced by one cell module as shown in FIG. 24 is extremely small, by laminating a large number of such cell modules 200, the desired electrical output is obtained. Accordingly, the first and second separators 206, 207 are provided to prevent the fuel gas and the oxidant gas from leaking to adjacent cells. They are called “separators” in this sense.
The first separator 206 has on its surface 206a the flow path 208 for fuel gas, while the second separator 207 has on its surface 207a the flow path 209 for oxidant gas. However, it is necessary for gas to effectively contact the anode side electrode 202 and the cathode side electrode 203. Therefore, it is necessary for the flow paths 208, 209 to provide a large number of extremely shallow grooves.
Further, each of the first and second separators 206, 207 have a fuel gas supplying hole portion 210a and an oxidant gas supplying hole portion 211a at one end portion thereof, and also each have a fuel gas discharging hole portion 210b and an oxidant gas discharging hole portion 211b at the other end portion thereof. Further, each of the first and second separators 206, 207 have a cooling water supplying hole portion 212a for making cooling water pass through at one end portion thereof, and have a cooling water discharging hole portion 212b at the other end portion thereof.
The present inventors have variously tried to manufacture a cell module by sandwiching a membrane electrode assembly formed from electrolytic films and electrodes by two separators, by coating a liquid sealant in place of the gaskets 204, 205 on the separator. However, the problems shown in FIGS. 25A through 25D arose.
FIGS. 25A through 25D are operational views illustrating a method for coating a sealant on the separator for fuel cell. More concretely, FIG. 25A is an operational view showing a state before a coating-start and a coating-end of the sealant are connected; FIG. 25B is an operational view showing a state in which the coating-start and the coating-end of the sealant are connected; FIG. 25C is an operational view showing a state before the coating-start and the coating-end of the sealant are overlapped; and FIG. 25D is an operational view showing a state in which coating-start and coating-end of the sealant are overlapped.
As shown in FIG. 25A, when a sealant 223 is coated on a separator 221 by a sealant coating gun 222, if an attempt is made to connect the coating-end portion to the coating-start portion 224 of the sealant 223, as shown in FIG. 25B, a space 226 comes into being between the coating-start portion 224 and the coating-end portion 225.
Further, as shown in FIG. 25C, if an attempt is made to overlap on coating-start portion 227 of the sealant 223, as shown in FIG. 25D, spaces 221, 232 come into being between the coating-start portion 227 and the overlapped portion 228 of the sealant 223.
Therefore, the fuel gas, the oxidant gas, and water leak from the cell interior, and sufficient performance of the fuel cell cannot be obtained.
Moreover, another problem as shown in FIG. 26 arose.
FIG. 26 is an operational view illustrating the sealant coating procedure. When the sealant 223 is coated on a separator 221 by a sealant coating gun 222, if the driving portion of the sealant coating gun 222 is stopped in order to end the coating at the coating-end portion 225 of the sealant 223, there are cases in which the sealant 223 which remains in a nozzle portion 234 of the sealant coating gun 222 drops down. This leads to deterioration of the sealant coating quality or deterioration of the sealability due to non-uniformity of the sealant thickness.
Furthermore, a problem as shown in FIGS. 27A and 27B arose.
FIGS. 27A and 27B are operational views illustrating the procedure of coating the sealant onto a warped separator. More concretely, FIG. 27A is an operational view showing a state in the midst of coating the sealant, and FIG. 27B is an operational view showing a state after coating the sealant.
FIG. 27A shows a state in which the sealant 223 is coated by the sealant coating gun 222 on the separator 221 placed on a placement platform 236.
In the separator 221, when grooves such as a gas flow path or the like are formed only on one side, or when differently shaped grooves are respectively formed on one side and the other side, there are cases in which warping arises as shown in the drawings.
If an attempt is made to coat the sealant 223 on such a warped separator 221 by the sealant coating gun 222, the distance between the distal end of the sealant coating gun 222 and the separator 221 is changed when the sealant coating gun 222 horizontally moves as shown by the outlined arrow. Therefore, as shown in FIG. 27B, for example, a sealant thickness th2 at the central portion of the separator 221 is smaller than a sealant thickness th1 at the edge of the separator 221. Therefore, there is the concern that gas and water will leak from the portion at which the sealant 223 is thin.